The (bad) assumptions

A model is only as valid as the assumptions behind it.  Most models are based upon certain "knowns" such as accepted no-stop time limits for the different depths.  But these time limits/tables are only valid if the diver performs the dive in the same manner the tables were tested.  Most tables were tested with only mild to no exercise being performed before, during or after the dive ... so their time limits would give a lower incidence of bubbling than what the diving public would probably experience.  So always dive conservative since you are more than likely to have more micronuclei and thus more bubbling after a dive than the acceptable limits of the table when doing the same dive as a table test subject (who was probably sitting around with very little activity waiting his turn to get in the chamber for his test dive).